Fixes a minor grammatical mistake in Readme.
Fixes a minor grammatical mistake in Readme.

nothingmagical/cheddar-ios,yzpniceboy/cheddar-ios,SuPair/cheddar-ios,jianwoo/cheddar-ios,yzpniceboy/cheddar-ios,iOSTestApps/cheddar-ios,jianwoo/cheddar-ios,liduanw/cheddar-ios,liduanw/cheddar-ios,iOSTestApps/cheddar-ios,SuPair/cheddar-ios